This invention relates to a new and improved thermal battery, and is particularly concerned with a thermal battery which is activated by external heating such as a fuel fire.
Thermally activated electrochemical cells are well known. Standard ordnance thermal batteries are activated by igniting an electric match, squib, or percussion primer inside the battery which initiates combustion of heat generating material. Heat from combustion is retained inside the battery by thermal insulation. This heat melts the electrolyte and activates the battery.
Previous methods of reducing hazard from ordnance exposed to detrimental heating include pyrotechnic sensors that react chemically to provide heat and/or flame. Such sensors are intrinsically less reliable than sensors which provide an electrical signal or electrical energy.
Power generating devices utilizing a source of heat for activation are disclosed, for example, in U.S. Pat. Nos. 4,700,009 to Iden, 3,946,675 to Stalfors, 4,338,560 to Lemley, and 3,425,872 to Levy.
One object of the present invention is the provision of a thermal battery activated by heat from an external source.
Another object is to provide a thermal battery which operates without an internal initiating mechanism or heat generating materials and which may not utilize thermal insulation.
A still further object is the provision of an improved efficient thermal battery of the above type, constructed of readily available components, and particularly adapted to reduce hazards from ordnance such as missiles and rockets exposed to detrimental heating.